The present invention relates to an X-ray crystal orientation measuring method and an X-ray crystal orientation measuring apparatus, for measuring an orientation of a crystal with using X-ray.
An orientation measurement for a crystal can be applied to a single crystal material. And, such the measurement of the crystal orientation is made for studying on the direction of growth of the crystal axis, in particular, with respect to an outer configuration of the crystal, and in that instance, in general, there are already known a method for determining all of the orientations in three (3) axes and also a planner-orientation measurement for studying a direction of a normal line on a specific lattice plane.
The present invention relates, in particular, to such the planner-orientation measurement, and this planner-orientation measurement is applicable when full three (3) axis orientation is known by or from outer configuration due to habits and/or cleaves of the crystal, and therefore it is applied in a case when trying to cut the crystal, accurately, on a specific surface thereof. A representative one of this is a method, being so-called “Cut Surface Inspection Method”, for example.
However, the single crystal mentioned above differs in the mechanical, optical and/or electro-magnetic characteristics, depending upon the crystal orientations thereof (i.e., having an anisotropy). For that reason, in order to utilize such the characteristics of the crystal in positive manner, the single crystal must be studied upon the crystal orientation thereof, in advance, and must be cut out into a desired direction (such as, cutting at a specific orientation), to be used. For that purpose mentioned above, also, the crystal orientation measurement is necessary, to which the present invention relates.
By the way, in the Patent Document 1, which will be mentioned below, there is already known a method and an apparatus thereof, wherein a measurement is made upon an incident angle of X-ray, at which the Bragg reflection occurs, with using a characteristic X-ray, and this operation is conducted in four (4) directions, each separating by 90 degree in the angle, or alternately, two (2) directions, each separating by 180 degree in the angle, upon a surface of the crystal plate, thereby measuring the required planner orientation from the already-known Bragg angles. However, such planner orientation measuring apparatus is already available on markets, as a product of applying such the measurement method therein, such as, by the name of “FSAS” or “SAM”, for example.
And, there is also already known a method for measuring the crystal orientation, through measuring an incident angle of the X-ray where the Bragg reflection occurs with using the characteristic X-ray, as well as, studying upon which position the diffracted X-ray is incident, at the same time, in Patent Document 2, which will be mentioned below.
Patent Document 1: Japanese Patent Publication No. Hei 4-59581 (1992) (corresponding JP Laying-Open No. Sho-57-136151 (1982)), and in particular, FIG. 3 thereof; and
Patent Document 2: Japanese Patent Publication No. Hei 3-58058 (1991) (corresponding JP Laying-Open No. Sho-57-136150 (1982)), and in particular, FIG. 4 thereof.
However, with such the method relating to the conventional arts mentioned above, it is indispensable to make an operation, i.e., scanning the X-ray at the incident angle (angle ω) thereof within a predetermined region. And, if the crystal is chained in the kind thereof or in the lattice plane index thereof, for example, since the diffraction angle 2θ thereof also changes, therefore it is necessary to set up an optical system for measurement, again, for each time. For this reason, there is a drawback that it is necessary to provide a complex mechanism, such as, a scanning mechanism, thereby bringing the apparatus itself to be expensive in manufacturing. In particular, with the method of the Patent Document 1 mentioned above, since the scanning must be made four (4) times or two (2) times, and since it is necessary to make determination upon upper and lower positions of the diffracted ray, therefore there is a drawback that it takes a time for the measurement. Also, with the method known by the Patent Document 2 mentioned above, after the scanning ω, since it is necessary to study the position on the detector, where the X-ray is incident upon, while returning this angle ω to a peak value to be fixed thereat; therefore, there is also a drawback or problem that it takes a time for the measurement.
Further, with the method of the Patent Document 1 mentioned above, it is assumed that a target of measurement is a single domain; i.e., the crystal, in which atoms or molecules are disposed or arranged, regularly and cyclically, and therefore the crystal orientation is directed always in the same if studying thereof in any position of the crystal. Then, if applying the method to other crystals having the structures, such as: the sub-grain structure <i.e., the crystal, with which it is difficult to obtain such the single domain as was mentioned above, and it is made up with a large number of crystal grains, for example, crystal of fluorite (CaF2), crystal of magnesia (MgO), crystal of ferrite, etc. >; the lineage structure<i.e., it is a kind of defective structure, so that it may show a behavior, depending on the position, that the orientation of the crystal changes continuously. For example, this can be found in sapphire of oxide crystal, LN (Lithium Niobium Oxide: LiNbO3), LT (Lithium Tantalum Oxide: LiTaO3), etc.>, there may occur a case where the X-ray does not irradiated upon the same position on the crystal in the operations of four (4) times or the two (2) times of scanning of the angle ω; therefore, there is a drawback of coming out an erroneous result therefrom.
And, in particular, when measuring a distribution of the orientations on the crystal having such the sub-grain structure and/or the lineage structure, other than the single domain, there is a necessity of so-called a mapping measurement, i.e., for measuring the orientation at plural numbers of measuring points upon the measuring surface thereof. For this reason, with such the methods already known by the above Patent Documents 1 and 2, as is apparent from the method mentioned above, a considerable long time is necessary only for one (1) time of measurement itself (i.e., the measurement at one (1) point), therefore, in particular, in a case when trying to make the measurement of the orientation at a large number of measuring points, through the mapping measurement, there is the drawback of taking an expansively large amount of time.